How Hot Is Betelgeuse Compared to the Sun?

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Betelgeuse is 4,000 degrees Fahrenheit cooler than the sun, measuring an effective temperature of 6,000 degrees Fahrenheit compared to the sun's 10,000 degrees Fahrenheit. Despite its lower temperature, Betelgeuse's diameter of 600 million miles is around 700 times the diameter of the sun. Betelgeuse receives a large amount of attention from scientists due to several unanswered questions about its composition and movements.

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Betelgeuse is a red supergiant in the M classification, meaning that it appears light orange and red to the human eye. The star emits 7,500 times as much energy as the sun. As a red supergiant, Betelgeuse is likely much closer to the end of its life than the sun, a G-type white dwarf. Betelgeuse is 520 light-years from Earth, and is visible in the constellation Orion.

The relatively cool temperature on Betelgeuse remains a puzzle to astronomers. Scientists have yet to determine why the gasses leaving the star are much cooler than expected, as well as how Betelgeuse’s large mass is sustainable at such low temperatures. Several scientists have proposed that these temperatures can be explained by the presence of a large magnetic field, or a series of shockwaves reverberating through the star, but further observation will be necessary to determine the cause of Betelgeuse's cool temperatures.

Astronomers are also interested in Betelgeuse’s highly variable diameter. While its diameter is on average 700 times greater than that of the sun, it regularly expands and contracts in dramatic fashion. This means that its diameter can shift to be between 550 and 920 times greater than the sun.

Another question astronomers and scientists have about Betelgeuse has to do with the speed of its rotation. The star rotates at a very high speed, which is unusual because of its high mass. Some scientists have speculated that the high rate of rotation was initiated 100,000 years ago when Betelgeuse absorbed another star.

Betelgeuse is also notable to astronomers due it its impending collision with an interstellar dust cloud in several thousand years. Observations of the star have led scientists to predict that it will collide with this mass of interstellar dust at a speed of 66,960 miles per hour. It’s predicted that the edge of the star will begin colliding with the cloud in approximately 5,000 years, and the cloud will reach the star’s center 12,500 years later.